The invention relates to scented ink compositions for ink jet printers which generate aromas from the printer during operation and scented printed articles produced therefrom.
The pleasing effects of fragrant substances has lead to many products and methods for providing pleasant aromas to the olfactory senses such as perfumes, oils, soaps, lotions, creams, aromatic candles, room fresheners, potpourri, etc. In recent years there has been an increased interest in fragrances by those who believe the aromas from essential oils have therapeutic effects. The use of such oils is commonly referred to as aroma therapy but therapeutic benefits beyond the pleasing effects of their aroma has not been recognized by the FDA.
Apparatus for releasing fragrant aromas into a room have varied widely from manual to automatic dispensers such as the apparatus described in U.S. Pat. Nos. 2,618,892; 3,400,890 and 4,484,768 and the battery operated aerosol, gel and pump air fresheners of AIR DELIGHTS.TM. of Portland Oreg.
The media from which fragrant substances are released has also varied widely from liquids, gels, solids and aerosols. The diffusion of fragrant vapors from polymers described in U.S. Pat. No. 3,567,119 is one example. The use of scented inks, paints and marking compositions (crayons) to prepare scented articles is well known as described in U.S. Pat. Nos. 2,578,425; 5,474,805 and 5,577,947. These inks, paints and marking compositions have been adapted for printing methods other than ink jet printing.
Ink jet printing has experienced a significant increase in use in recent years due to reduced equipment cost, color availability and improvements in print speed and print resolution. There are two major categories of ink jet printing--"Drop-on-Demand" and "continuous" ink jet printing. For continuous ink jet printing, a conducting ink is supplied under pressure to an ink nozzle and forced out through a small orifice. Prior to passing out of the nozzle, the pressurized ink stream proceeds through a ceramic crystal which is subjected to an electric current. This current causes a piezoelectric vibration equal to the frequency of the AC electric current. This vibration, in turn, generates the ink droplets from the unbroken ink stream. The ink stream breaks up into a continuous series of drops which are equally spaced and of equal size. Surrounding the jet, at a point where the drops separate from the liquid stream in a charge electrode, a voltage is applied between the charge electrode and the drop stream. When the drops break off from the stream, each drop carries a charge proportional to the applied voltage at the instant at which it breaks off. By varying the charge electrode voltages at the same rate as drops are produced it is possible to charge every drop to a predetermined level. The drop stream continues its flight and passes between two deflector plates which are maintained at a constant potential. In the presence of this field, a drop is deflected towards one of the plates by an amount proportional to the charge carried. Drops which are uncharged are undeflected and collected into a gutter to be recycled to the ink nozzle. Those drops which are charged, and hence deflected, impinge on a substrate traveling at a high speed at right angles to the direction of drop deflection. By varying the charge on individual drops, the desired pattern can be printed.
In a typical "Drop-on-Demand" ink jet printing process, a fluid ink is forced under pressure through a very small orifice of a diameter typically about 0.0024 inches in the form of minute droplets by rapid pressure impulses. The rapid pressure impulses are typically generated in the print head by either expansion of a piezoelectric crystal vibrating at a high frequency or volatilization of a propellant within the ink by rapid heating cycles. The piezoelectric crystal expansion causes the ink to pass through the orifice as minute droplets in proportion to the number of crystal vibrations. Thermal jet printers employ a heating element within the print head to volatilize a propellant and form droplets in proportion to the number of on-off cycles for the heating element. The ink is forced out of the nozzle when needed to print a spot on a substrate as part of a desired image. The minute droplets may be energized to achieve an electrical charge and deflected as in the continuous ink jet printing. Conventional ink jet printers are more particularly described in U.S. Pat. Nos. 3,465,350 and 3,465,351.
Another type of ink jet printing process is an electrostatic ink jet process which employs an electrostatic field to draw the ink through the nozzle to the substrate. Charged ink droplets are drawn to an oppositely charged platen behind the receiving substrate. Such devices have been developed by Technology International Corp. of Boulder, Colo., under the trade name ESIJET.TM..
To operate satisfactorily within an ink jet printer, the ink has many requirements. The ink must exhibit low viscosity values (preferably below 20 centipoise at 25.degree. C.), contain no large particulate matter (typically below 5 .mu.m), and be sufficiently stable so as not to dry and clog the jet orifice when not in use. For "continuous" ink jet printing, the ink must be conductive with a resistivity value typically below 10,000 ohms and the unused ink is preferably recyclable. Secondary factors must also be considered, such as avoiding the generation of flammable vapors during use and minimizing the impact on the environment.
Operating satisfactorily within an ink jet printer addresses only some of the requirements of the ink. The ink must also dry rapidly and bond to the substrate to which it is applied such as coated and uncoated papers to provide printed images or indicia without smearing.
These inks sometimes do not contain a binder for the pigment or dye therein and these pigments or dyes to must be absorbed into the surface of the print medium to provide stable printed images or indicia. Some of the requirements of jet printing inks are described in U.S. Pat. No. 4,258,367.
It is desirable to provide jet inks with more versatile properties. It is also desirable to provide a simple means for dispensing fragrances and for forming scented printed articles such as greeting cards with fragrant printed images and indicia.